Dry stencil



Patented July 16, 1929.

UNITED STATES HENRY H. HAWLING, QF RIDGEFIELD PARK, NEW JERSEY.

DRY STENCIL.

No Drawing.

This invention relates to a dry stencil of bare type of a writing machine, without previous moistening, and then used on duplicating or addressing machines, or the like, for the reproduction of typewritten matter. It

is also adapted for reproduction of drawings and the like.

An object of the invention consists in providing such a stencil which is easily handled and read by the operative, and in which the letters cut by the typewriter are uniform and distinct.

Another object consists in providing such a stencil that is cheap to manufacture. durable in use, and which may be folded and filed without injury or rapid deterioration.

Another object consists in providing certain improvements in the composition whereby the above named and other objects may effectively be attained.

The stencil comprises a base of porous fibrous material such, for instance, as a thin Japanese tissue paper, commonly known as Yoshino, that is in general use as a base for stencils.

The said base is treated so as to be impregnated and coated with the composition that imparts to it stencilizing properties. This composition is preferably made in liquid form so that it can be applied to the base material by dipping, or by rollers, or by brushing, suitable methods of application being well understood by operatives in this industry.

i The composition includes casein, sodium hydroxide, sodium tungstate. glycerol, and water, or their equivalents, I prefer to use casein which is commercially pure, and which is commonly referred to as washed casein.

A practical formula 1s as follows Casein (washed) 100 grams Sodium hydroxide 5 grams. Sodium tungstate 4 grams. Glycerol 60 grams. Water 800 0.0.

The foregoing proportions are subject to variation under different circumstances, but will serve as a practical basis for operation by one skilled in the art.

In making up this mixture, I prefer to proceed as follows:

The sodium hydroxide is dissolved in a Application filed October 21, 1927. Serial No. 227,864.

portion of Water, 100 c. c. of Water being satisfactory for this step. Next the sodium tungstate is dissolved in the said mixture of sodium hydroxide and water.

The mixture is then placed in a mortar and the casein thoroughly ground into it with a pestle, or the like.

Thereafter, the glycerol is added.

The remaining 200 c. c. of water may then be added and the whole mixed thoroughly and heated on a water bath, at a temperature about 100 C. until solution of the casein is obtained.

The mixture should then be filtered and is ready to be used for the purpose of impregnating or coating the paper base, which step should be carried out while the mixture is still hot. For the purpose of impregnating or coating, the paper may be dipped into the liquid mixture manually, and, on withdrawing therefrom, passed in contact with a wire or straight edge to remove the excess liquid,

and hung to dry. Another suitable way is to have rollers dipping into the liquid and to pass the paper in contact with one or more rollers which have been rotated in the liquid so as to cover their surfaces therewith; after which the excess may be removed, as before, and the sheet hung to dry. A somewhat cruder way of impregnating or coating the paper is to lay it on a smooth surface, such as glass, and brush the mixture thereon, after which the excess matter may be removed and the sheet hung to dry as before. In either case, the drying operation may, if desired, be performed by an air bath at a temperature not exceeding 100 centigrade.

While I have described, with some detail, the proportions of the ingredients, the order of the steps in which they are mixed, the conditions under which the steps are carried out, and the way in which the paper is impregnated or coated, I would say that the several details can bev varied without departing from the spirit and scope of my invention. For instance, the percentage of the glycerol may be varied according to the climatic conditions where used, the temperature of storing the stencil paper or the completed stencils, or other factors that may tend to vary the moisture content. The percentage of sodium tungstate may be varied according to the hardness or toughness of the pafper desired. The compound or conjugate ormed by the sodium hydroxide and the casein may also be varied by changing the relative proportions of these substances, so as to obtain a mobile or an increasingly viscous liquid. The proportions heretofore given Will furnish a stencil paper having properties satisfactory for average use.

It is my belief that the sodium hydroxide has a tendency to toughen the fiber of the paper base by a sort of mercerizing action, and that the sodium tungstate serves to toughen the casein. I attribute the desirable characteristics of this stencil in part to these two features.

After the sheets have dried, they may be cut to suitable size and placed on backings or on card board frames, in the usual way. When it is desired to use them, they may be cut or Written on a typewriter in a manner familiar to the art, and then supplied to duplicating machines or addressing machines, as the case may be, and used in the ordinary l t should be noted that, although this invention is primarily directed to the production of a dry stencil, the stencil thus produced may be used also as a Wet stencil, in which case the stencil, before cutting on the typewriter, may be moistened with Water after the manner commonly understood and practiced in this art. In this application, the article has certain advantages over those previously devised because of its low cost of production and the heaviness and firmness of ,treated With a composition,

the coating on the Japanese paper which promotes clear reproduction.

In view of the fact that various changes may be resorted to, it will be understood that I do not intend to be limited to the details herein described, except as they may be included in the claims, and that I intend the recitation of particular elements in the claims to include their equivalents.

What I claim is:

1. A type impressible stencil having a base treated With a composition,said composition including casein and sodium tungstate.

2. A type impressible stencil having a base treated With a composition, said composition including casein, sodium hydroxide and sodium tungstate.

3. A type impressible stencil having a base treated with a composition, said composition inciiuding casein, sodium tungstate, and glycero 4. A type impressible stencil having a base treated with a composition, said composition including casein, sodium hydroxide, sodium tungstate, and glycerol.

5. A type impressib'le stencil having a base said composition including casein, an alkali-hydroxide, and sodium tungstate.

In testimony, that I claim the foregoing as my invention, 1 have signed my name this 19th day of October, 1927.

HENRY H. HAWLING. 

